A man is reflected on a screen showing the prices of bitcoin at Bithumb cryptocurrency exchange in Seoul on Wednesday. Bithumb, South Korea's second-largest exchange, said US$31 million worth of virtual currencies have been stolen by hackers, the latest in a series of recent hacks targeting digital currencies. Photo: AP

A man is reflected on a screen showing the prices of bitcoin at Bithumb cryptocurrency exchange in Seoul on Wednesday. Bithumb, South Korea's second-largest exchange, said US$31 million worth of virtual currencies have been stolen by hackers, the latest in a series of recent hacks targeting digital currencies. Photo: AP